This invention relates to ultrasonic imaging methods such as diagnostic medical ultrasonic imaging methods, and in particular to improved transmit signal generators for such methods.
Hwang U.S. Pat. No. 5,706,819 and Chapman U.S. Pat. No. 5,632,277 disclose additive inverse techniques for selectively removing fundamental components of an ultrasonic image. In the disclosed methods, two or more ultrasonic pulses are transmitted into a subject along the same beam direction, including first and second pulses of opposite polarity. The echo signals associated with the first and second pulses are summed, thereby causing linear components to cancel to a greater extent than non-linear components. For example, fundamental frequency components of the echo signal associated with linear propagation and scattering are selectively canceled, and second harmonic components of the echo signal due to non-linearities are enhanced.
The present invention is directed to improvements to such additive inverse processing methods.